Impact tests are used to evaluate the toughness of welds. Toughness is measured by the amount of energy required to cause an item to fracture and fail.

This test involves striking a standard specimen with a controlled weight pendulum travelling at a set speed. The amount of energy absorbed in fracturing the test piece is measured and this gives an indication of the notch toughness of the test material.

A brittle material will absorb a small amount of energy when impact tested, a tough ductile metal a large amount of energy.